Not quite sure how to explain it but whenever i start to slow down or im stopped while in drive my engine starts to run very rough to the point where it shakes my whole truck. When i hit the gas its rough through lower rpms but once i get to higher rpms its not as bad. Also when im in park the engine seems to run a lot better but its still more rough running than usual. Anyone have an idea on what could be causing this? Your help is much needed and very much appreciated!